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Obesity Does Not Protect From Loss of Lean Tissue During Weight Loss



One of the biggest challenges during weight loss is the maintenance of lean body mass. In this regard, I have previously blogged about the importance of maintaining adequate protein intake even when restricting overall caloric intake. (Another important measure in this regard is resistance training).

A common misconception appears to be that obese people have enough stored energy to live off so that one can confidently reduce their caloric intake to help them lose weight – the fewer calories the better.

Nothing else can be further from the truth – as it turns out, obese individuals are just as, if not more, prone to losing lean tissue (mainly skeletal muscle) as are lean individuals.

This is nicely demonstrated in a study by Gregory Henderson and colleagues from the Mayo Clinic, just published in the journal Obesity.

In this study, whole body protein metabolism was studied in twelve obese women over a wide range of BMIs using leucine-tracer techniques following five days of a weight-maintaining diet and then after 30 days of a 1,400 kcal deficit with maintained protein intake.

Before weight loss, when expressed as total rates, per body weight (BW) or per fat-free mass (FFM), leucine rate of appearance (Ra), and nonoxidative leucine disposal (NOLD) were significantly higher in the heavier individuals indicating higher protein turnover.

Nevertheless, caloric restriction reduced protein turnover and oxidation to the same extent in obese and non-obese individuals showing that higher fat mass does not favorably alter the response of protein metabolism and clearly does not mitigate the loss of lean body mass with caloric restriction.

As any loss of lean body mass, a key determinant of resting metabolic rate, would be counterproductive both by limiting weight loss and by facilitating weight regain, it is indeed essential to maintain or perhaps even increase protein intake when reducing overall caloric intake.

The notion that obese people have enough stored calories and can therefore easily go without adequate protein intake (or perhaps no food at all) for a few days is plain wrong.

Happy to hear of any experiences with excessive lean body mass during weight reduction and prescribed measures to limit this loss.

AMS
Hamburg, Germany

8 Comments

  1. Hi Arya,
    I noticed that relative to the amount of body fat lost (8%) the severely obese patients lost a high amount of lean tissue (6%). What is interesting to me is why this is not the case immediately 1 month following gastric bypass surgery (body fat loss was 12% but lean body mass only 5%). I don’t think is has to do with the high amounts of protein intake (~20%) following surgery, since protein intake was seems sufficient in the study. It really is a paradox to me give the surgical trauma etc.

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  2. Gotta get my head around this one.

    Suppose a weight maintaining diet (ignoring other nutrition needs for simplicity) is:

    x oz grains, y oz meat, z oz veggies.

    A diet which recommends “eat good food, but in smaller portions” would be

    80% of x oz grains, 80% of y oz meat, 80% of z oz veggies

    That wouldn’t work, because the protein component (meat) is only 80% of what is needed. The dieter will lose lean muscle mass. The dieter needs to keep protein in diet, for example:
    80% of x oz grains, 100% of y oz meat, 80% of z oz veggies

    “…higher fat mass does not … mitigate the loss of lean body mass with caloric restriction.” I think I got that – having body fat to lose won’t protect you from losing muscle, and even having a lot of extra body fat still won’t protect you from losing muscle.
    Many people figure that when you go on a calorie restricted diet, the body just burns up the extra fat, not burning up muscle until the fat is gone.

    Look at all the “healthy” diets that are based on filling up on vegs,
    for example:
    80% of x oz grains, 80% of y oz meat, 200% of y oz (low cal) veggies
    That would still lead to loss of muscle, even though it has large quantities of healthy veggies.

    If I get this right, you can have an admirably bulging bicep, but unless it receives a continual input of a certain amount of protein (and it exercises) it will waste away. This would happen even if the person ate enough calories from non-protein sources to maintain weight.

    Do I have that right – people lose muscle because when they reduce calorie intake they also coincidentally reduce protein intake below the minimum level muscles need daily?

    Is there also something about the body being in a calorie deficit that means the body doesn’t metabolize its 100% of z oz meat properly any more, so that even the amount of protein that used to be enough to maintain muscle isn’t sufficient when the person is on a calorie restricted diet?

    Then you’d need
    70% of x oz grains, 120% of y oz meat, 70% of z oz veggies
    Not only are the total calories reduced, the balance of food has to be different to keep protein high while reducing total calories.
    (I know my numbers aren’t exact – just illustration of general idea)

    This is very significant to me because my doctor sent me to a hospital dietitian for a weight loss program, and the plan she gave me was to “Eat a balanced diet by following the Canada food guide (which maintains a healthy weight), but make each portion smaller than usual”. She said NOTHING about keeping up protein intake.
    This is DOCTOR recommended, HOSPITAL-BASED advice. I reduced portion sizes of all food groups, including protein group (actually fish, beans, eggs, etc, not just meat), except I ate extra low cal veggies from the veg-and-fruit group.

    If I am understanding this post correctly, I am actually sabotaging my weight loss efforts by reducing my protein intake along with everything else.

    Are there any official guide lines for DOCTOR PRESCRIBED, HOSPITAL-BASED weight loss diets that would require such diets to maintain protein intake and counsel patients on why this is important?

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  3. It took me a long time to get my head around this as I was living through it. I didn’t understand why a 600 pound guy didn’t have all kinds of energy because of my excessive body mass and storage of excess fat. I truly always thought that I just need to eat less and move more and everything will fall into place. As I gained more and more strength my personal trainer hammered the point to me that I needed protein to stimulate muscle regeneration and to minimize lean muscle loss.

    He nailed it and so did I. I have consistently worked out with weights while losing weight and have not only shed the weight and maintained consistent numbers but have also significantly increased muscle mass. I recognized the importance of additional protein supplementation and have done so with protein shakes before and after workouts. I was always told that it is nearly impossible to lose weight and gain muscle at the same time but if you’re educated and consistent you can do both! Great article Dr. Sharma!! Well…..off to the gym!!!!

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  4. I have analysed many patients on our strength training program and I recommend a supplement of 25 grams of protein per day (low fat food when possible) for everyone unless their doctor disagrees. BUT even with a steady intake of protein, calorie consumption below resting metabolic rate will stimulate metabolism of lean tissue unless muscle conditioning is accompanied with adequate protein intake. In post baritraic patients, kcal intake is highly reduced HOWEVER all the hospitals supplement with not only protein but large doses of calcium and other minerals. I beleive it is this combination of supplementation that prevent early onset lean tissue wasting. Unfortunately it does not last long and many patients 1 and 2 years post can see up to 40% lean tissue loss. Most have stopped the supplementation regimen and many never get on an exercise program. Plenty of room for study!

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  5. It is important to note here that while protein intake is certainly important, resistance exercise is now actually thought to DECREASE protein needs for muscle retention in young healthy individuals. Of course, this work may not be directly applicable to an obese population, but I can’t see why this would not be the case. (Acutely protein demands increase for about 2 weeks, but decrease thereafter.)

    Adding resistance training to a weight loss program (as Dr. Sharma mentioned in his post) could also mitigate some of the lost muscle tissue due to caloric restriction.

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  6. >Mark
    I certainly agree on the importance of resistance training and certainly recommend this to any patients undergoing weight loss (and thereafter).

    AMS

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  7. I’m quoting secondhand information that I’ve gleaned from my go-to source for diet (and protein!) information: Lyle McDonald at bodyrecomposition.com. Anyway, the basic idea of a psmf (protein-sparing modified fast) is that when you reduce calories, your body doesn’t automatically use fat stores alone but also muscle; eating protein prevents the muscle breakdown. I think the biological idea is that breaking down fat stores uses protein? Or because the body under stress of any kind needs more protein to deal with it? in any case, just like a psmf is better than a simple fast for dropping fat without muscle loss, any weight loss diet is best with a higher protein intake. 2.2g protein/kg of LBM is pretty much the dieting recommendation. In my personal case, not obese, I find that dieting by simple caloric restriction results in a loss of 1 pound of muscle for each 2 pounds of fat; with high protein intake I lose closer to 1 pound of muscle for each 9 pounds of fat loss

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  8. My dad, who’s in his mid-seventies and has congestive heart failure, has been on a diet and has been losing weight. I haven’t said anything, but I have wondered if it’s good for him or not, partly because I’ve noticed a pattern of people losing a lot of weight before dying. I’d like to read it this study myself, but your discussion of it makes me feel a bit better.

    However, I’m still worried about what will happen when (if) he regains the weight. He can’t exercise, so I’d imagine that he’s losing lean mass. The heart is a muscle and I’d guess that his heart in shrinking as he loses weight. If he regains, will his messed-up, shrunken heart be able to manage the challenge? Did this study continue long enough to include hard outcomes after weight regain?

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